Time-of-flight (TOF) nuclear imaging, such as TOF positron emission tomography (PET), is used to construct two-dimensional and/or three-dimensional images of structures within a patient. TOF PET (and other TOF nuclear imaging) detects coincidence events representing near simultaneous detection of annihilation photon pairs using a pair of detectors. The TOF PET system determines the difference in time between the detection of the two photons (e.g., the time of flight) and localizes the point of origin of the annihilation event that occurred between the two detectors.
Silicon photomultipliers (SiPM) have been proposed as detectors for use in nuclear imaging, such as in TOF PET. SiPM are single-photon avalanche diode (SPAD) devices connected in an avalanche photodiode array. Analog SiPM (aSiPM) devices intrinsically have a large terminal capacitance, which determines the total input capacitance and large quenching resistance. The quenching resistance is related to input impedance of the analog frontend electronics (AFE) coupled to the aSiPM device. The large terminal capacitance and large input impedance results in a slow time response for aSiPM-based detectors.